Drive mechanism



(5- D. FREDELL March 24, 1970 I DRIVE MECHANISM 3 Sheets-Sheet 1 FiledAug 5, 1967 9 o I 2 I p 'qlllll mnmrlllll INVENTOR. GARY D. FREDELL ATTR NEYS.

March 24, 1970 e. n. FREDELL 3,501,968

DRIVE MECHANISM Filed Aug 5, 1967 3 Sheets-Sheet 3 mum FIG.2

MI 4/// INVENTOR.

GARY D. FREDELL ATTORNEYS March 24, 1970 e. D. FREDELL 3,501,968

DRIVE MECHANISM Filed Aug 5, 1967 5 Sheets-Sheet 3 FIG.4

FIG.5

INVENTOR. GARY D. FREDELL NEYS.

United States Patent US. Cl. 74-128 9 Claims ABSTRACT OF THE DISCLOSUREA shaft supporting a ratchet wheel is rotatably supported in a framewith a pawl reciprocating into and out of engagement with the teeth ofthe ratchet, thereby to impart rotation to the shaft. Lock meanscooperate with the pawl and the ratchet wheel to restrict rotation ofthe ratchet wheel with each'actuation to a predetermined amount in asingle direction with the ratchet wheel being otherwise restricted fromany movement in either direction. 1 I Y 1 This invention is directed toa drive mechanism, and more particularly to a mechanism in whichreciprocating linear motion is converted to rotary motion.

A great number of prior art mechanisms have been developed in whichreciprocating linear motion is converted to rotary motion. One type ofsuch prior art mechanisms employs a ratchet wheel on a shaft, a pawlwhich is adapted to engage the teeth on the ratchet wheel and someappropriate mechanism to reciprocate the pawl into and out of engagementwith the ratchet teeth. The path of reciprocation of the pawl isnormally tangential to the ratchet wheel and as the pawl approaches theratchet wheel it engages a ratchet tooth and rotates the ratchet wheel apredetermined amount. One advantage of a mechanism such as this is thata predetermined incremental rotation may be imparted wi.h a relativelysimple mechanism.

The prior art has also devised means to prevent unwanted rotation of theratchet wheel. Typically, the prior art approach has employed some formof a locking dctent or pawl which engages the ratchet wheel to preventreverse rotation of the wheel. These locking detents or first positiongenerally beneath the feedboard to a second engagement with the teeth ofthe ratchet wheel but are permitted to ratchet over the teeth as theratchet wheel is rotated by the drive pawl. As the drive pawl isreturned to its normal position to pick up the next tooth on the ratchetwheel, the lock detent or pawl remains in engagement with the teeth ofthe ratchet wheel and precludes reverse rotation of the wheel.

Mechanisms such as those hereinabove described have some shortcomings.Thus, although the prior art has provided means for preventing reverserotation of the ratchet wheel, the prior art has made no provisionwhatsoever for restraining rotation of the ratchet wheel in the drivedirection. The locking detent or pawl is wholly ineffective to preventadditional rotation of the ratchet wheel in the drive direction since itis designed to ratchet over the teeth of the wheel when the wheelrotates in this direction. As a result, the ratchet wheel is normallyfree to rotate in the drive direction when the drive pawl is disengagedfrom the ratchet teeth. Indeed, in some such mechanisms even when thedrive pawl is in engagement with the ratchet teeth, the drive pawl doesnot prevent additional rotation of the ratchet wheel in the drivedirection. It will be appreciated that devices such as these are notsatisfactory when a carefully controlled movement of the drive wheel isdesired.

It is an object of this invention to provide a drive A lock pawl ispivotally 3,501,968 Patented Mar. 24, 1970 mechanism in whichreciprocating linear motion is COH- verted into rotary motion.

It is a further object of this invention to provide a drive mechanism inwhich the rotary motion of a shaft is controlled both in direction andamount of rotation.

It is a still further object of this invention to provide a drivemechanism in which a drive pawl is reciprocated into and out ofengagement with the teeth of a ratchet wheel, and in which means areprovided to prevent any rotation of the ratchet wheel when the drivepawl is disengaged from the ratchet teeth.

Another object of the invention is to provide a ratchet mechanism inwhich the ratchet wheel may not rotate more than a predetermined amountin one direction with each actuation of the mechanism.

It is another object of this invention to provide a drive mechanismwhich converts linear motion into rotary motion with the linearly movingmechanism serving to lock the rotary mechanism from movement during aportion of the linear cycle.

It is still another object of this invention to provide a drivemechanism in which linear motion is converted into rotary mo.ion and inwhich the mechanism is failsafe in that it is impossible for the rotarymechanism to rotate in any direction without a prederminted linearmovement.

More specifically, this invention broadly contemplates a shaftsupporting a ratchet wheel with the shaft being rotatably supported in aframe. A pawl is provided to reciprocate into and out of engagement withthe teeth of the ratchet, thereby, to impart rotation to the shaft. Lockmeans cooperate with the drive pawl to prevent ro:ation of the shaftbeyond a predetermined movement for each reciprocation of the pawl, andlock means cooperate with the ratchet wheel to prevent rotation of theratchet wheel in any direction when the drive pawl is disengaged fromthe ratchet wheel.

The preferred construction of the invention contemplates a framesupporting a shaft for rotation with a ratchet wheel secured to theshaft. A solenoid-operated reciprocating plunger is supported on theframe with a drive pawl carried by the plunger and which is adapted tobe reciprocated into and out of engagement with the teeth on the ratchetwheel. A guide is positioned adjacent the pawl and serves to limitmovement of the pawl in a direction radially away from the ratchetwheel. supported on the frame and is biased into engagement with thewheel to prevent reverse rotation of the ratchet wheel. In addition, theplunger carries a lock bar which engages the lock pawl when the drivepawl is disengaged from the ratchet wheel. This lock bar cooperates withthe lock pawl to prevent the lock pawl from being pivoted out ofengagement with the ratchet wheel, thereby, preventing rotation of theratchet wheel in any direction when the drive pawl is disengaged fromthe wheel.

Referring to the drawings wherein like reference numerals indicate likeparts in the various views:

FIGURE 1 is a sectional view through the drive mechanism.

FIGURE 2 is a top plan view of the drive mechanism of FIGURE 1.

FIGURE 3 is a partial sectional view similar to FIG- different portionof the operating cycle.

FIGURE 4 is a sectional view of a modified form of the invention.

FIGURE 5 is a sectional view of the modification of FIGURE 4illustrating the parts in a different position of actuation.

Referring now to the drawings, and particularly the embodiment of FIGURE1, the drive mechanism indicated generally by the reference numeral 10,is supported on a frame 11 which may be mounted on any supportingstructure. A shaft 12 is rotatably supported by bearings 13 in the frame11. The shaft 12 may carry on its one end an appropriate driving elementsuch as a gear 15. Secured to the shaft 12 is a ratchet wheel 16, on theperiphery of which there are formed a plurality of ratchet teeth .17.

A plate 18 is supported on the frame 11 and the plate, in turn, supportsa solenoid indicated generally by the. reference numeral 19. Thesolenoid includes a solenoid coil 20 and a solenoid plunger or armature21. A bottom stop 22 provides a bottom limit for the reciprocation ofthe plunger 21. The plate 18 includes an aperture 23 through which theupper end of the plunger 21 projects.

An upwardly opening bore or slot 24 is provided in the upper end of theplunger 21 and receives therein a pawl 25. A pin 26 pivotally supportsthe pawl 25 in the bore 24. A leaf spring 27 is secured at the inner endof the bore and is adapted to engage a flat surface 28 formed on theinner end of the pawl. The flat surface defines a chord on the otherwisecircular end of pawl 25 with one end 29 of the surface serving as afulcrum point against which spring 27 abuts. A lock bar 30 encircles theupper end of plunger 21 and is secured thereto with a spring 31 receivedover the plunger 21 and interposed between the lock bar 30 and the uppersurface of the plate .18 to bias the plunger 21 in a direction away fromthe bottom stop 22.

As an upper stop. for the plunger 21, there is provided a stop bar andguide 33 which issupported by the frame 11. A guide block 34 is securedto the guide 33 with the guide block extending between a bifurcatedportion of lock bar 30 defining arms 35.

The pawl 25 is defined by substantially parallel opposed sides with abeveled surface 37 formed on the outer extremity of the pawl 25 defininga nose 38 adapted to engage the ratchet teeth 17 in the manner shown inFIGURE 1. As will be understood by those in the art, reciprocation ofthe plunger 21 will cause the pawl 25 to be reciprocated therewith, andas the pawl engages the ratchet teeth 17 on the ratchet 16, a rotarymotion will be imparted to the shaft 12.

In many applications it is desirable to prevent reverse rotation of theratchet wheel 16. Moreover, it is often desirable to assure that theratchet wheel 16 is advanced but a predetermined amount with eachactuation of the mechanism.

As a means to accomplish both of these purposes, there is provided alocking arrangement which includes a locking pawl or detent 40 which ispivotally mounted on a shaft 41 supported by the frame 11. The pawl isnormally biased by a spring 42 in a clockwise direction about the shaft41, as viewed in FIGURE 1. The pawl 40 includes a nose portion 43 whichis adapted to cooperate with the ratchet teeth 17. The pawl 40 furtherincludes a tail portion 44 which includes a flat surface 45 and atapered surface 46 adjacent surface 45. The tail portion 44 is of such aconfiguration and so dimensioned that it is normally spaced from thepath of reciprocation of lock bar 30 when pawl 40 is in engagement withratchet wheel 16.

The above-described mechanism operates in the following manner:

With the parts of the mechanism in the position shown in FIGURE 1, itwill be appreciated that the shaft 12 is effectively restrained from anyrotation. Thus, any tendency of the shaft 12 to rotate in the clockwisedirection will be restrained by the engagement of the pawl 25 with theratchet tooth 17. Similarly, the engagement of the pawl 40 with ratchetteeth 17 also prevents counter-clockwise rotation of the shaft 12. Thespring 42 maintains engagement of the pawl 40 with the ratchet wheel,while pawl 25 is maintained in engagement with the ratchet wheel by theblocking engagement of surface 36 on guide 33 with pawl 25.

When it is desired to impart rotation to the shaft 12, the solenoid 19is actuated which causes the plunger 21 to be drawn toward the bottomstop 22. As the plunger 21 is displaced, the pawl 25 is disengaged fromthe ratchet wheel, and the action of the spring 27 against the fulcrumoint 29 on the pawl causes the pawl 25 to pivot in a. counter-clockwisedirection around the pin 26. However, though the pawl 25 is nowdisengaged from the ratchet wheel 16, the shaft 12 is still restrainedfrom rotating in the clockwise direction due to the continued engagementof the pawl 40 with the teeth 17. Moreover, as the plunger 21 is moveddownward, the lock bar 30 moves to a position in which it is directlyopposed to the surface on tail 44 of the pawl 40. Thus, although pawl 40normally ratchets over teeth 17 when wheel 16 rotates counter-clockwise,lock bar 30 blocks pawl 40 so that it can no longer pivot to accommodatethe rotation of wheel 16, thereby effectively locking the ratchet wheelagainst movement in any direction.

As the solenoid is de-energized, the spring 31 returns the plunger 21 tothe position shown in FIGURE 1. As the plunger is returned to itsoriginal position, the pawl 25 picks up a different tooth of the ratchetwheel and imparts rotary movement to the shaft .12. Because the lock bar30 has now been displaced from a position of direct opposition to thetail portion 44 of the pawl 40, the pawl is free to pivot about theshaft 41 without interfering with the rotation of wheel 16.

It will be appreciated that this mechanism prevents any rotation of theshaft 12 from external sources and limits the rotation of the shaft to asingle ratchet tooth with each actuation of the solenoid 19. Themechanism is entirely failsafe in that all steps in the cycle theratchet wheel 16 is positively controlled by either the pawl 25 or thepawl 40 or both. Moreover, the engagement of the guide 34 with the lockbar 30 and arms 35 prevents any tendency of the plunger 21 to tilt sothat not only are the pawls locked in position, but also the plunger 21is restrained from movement.

Referring now to FIGURES 4 and 5, there is illustrated an alternateembodiment which achieves the same desirable results as the mechanism ofFIGURE 1. Essentially, the same basic arrangement of a frame, solenoidand plunger is employed. A shaft is rotatably supported by the frame anda pawl 51 is pivotably supported by a pin 52 carried by the upper end ofthe plunger. A

spring 53 biases the plunger to an extended position with,

a guide bar 54 functioning as an upper stop and a guide 55 cooperatingwith a bar 56 to prevent undesirable tilting of the plunger.

Rather than employing a single ratchet wheel as in the embodiment ofFIGURE 1, the embodiment of FIG- URE 4 employs two ratchet wheels. Thus,there are secured on the shaft 50 a ratchet wheel having ratchet teethformed around the periphery thereof. However, the teeth 59 on theratchet wheel 57 face in the direction opposite to the direction of theteeth 60 on ratchet wheel 58.

The pawl 51 includes a stepped shoulder 61 which is adapted to engagethe teeth 60 on the ratchet 58. The pawl further includes a nose portion62 which extends in a direction longitudinal of the pawl 51. Inaddition, the pawl includes an arm or lock bar 63 which is formed at theouter extremity of the pawl with the arm 63 having a transversedimension relative to the pawl 51. The arm '63 is adapted toengage theteeth 59 on the ratchet wheel 57. A spring 64 tends to bias pawl 51 inthe same manner as in the embodiment of FIGURE 1. The embodiment ofFIGURE 4 also includes a lock or check pawl 65 which cooperates with theteeth of ratchet wheel 58 to prevent reverse rotation.

The embodiment of FIGURE 4 functions in the following manner:

With the parts of the mechanism in the position illustrated in FIGURE 4,it will be appreciated that the shaft 50 is restrained from any movementwhatsoever. Thus, the tooth 60 on the ratchet wheel 58 in engagementwith the shoulder 61 of the pawl 51 is restrained from movement relativeto the pawl. Should the wheel 58 tend to rotate in a clockwisedirection, the check pawl 65 will restrain such tendency. In the eventthat the ratchet wheel should tend to rotate in the counterclockwisedirection, the tooth 60 will engage the longitudinal surface of theshoulder 61. Any tendency of the pawl 51 to be pivoted about the pin 52is prevented through the inter-engagement of the pawl with the lock bar54. Similarly, any attempt to tilt the plunger is restrained throughinterengagement of the lock bar 56 with the guide 55.

When it is desired to impart rotation to the shaft 50, the solenoid isactuated and the plunger is retracted in the manner of the embodiment ofFIGURE 1. As the plunger is retracted, the pawl 51 is disengaged fromthe teeth on the ratchet wheel 58. As the plunger is retracted, the pawl51 is permitted to pivot in a counterclockwise direction around the pin52'under the bias of spring 64. As the pawl 51 is pivoted in acounterclockwise direction, the arm 63 engages the teeth 59 on theratchet wheel 57. Any tendency of the shaft 50 to rotate in thecounterclockwise direction when the arm 63 is in engagement with theratchet wheel 57 will merely tend to move the plunger upward. However,since the plunger is electrically held energized, the shaft 50 isprevented from rotation. When the solenoid is de-energized, the plungerwill be displaced under the bias of spring 53 and the shoulder 61 on thepawl 51 will engage the next tooth on the ratchet wheel 58 and impart arotary movement to the shaft 50.

It will be appreciated that this latter embodiment may utilize theengagement of member 56 with check pawl 65 in the same manner as in theembodiment of FIGURE 1. However, since arm 63 is effective to preventrotation of shaft 50 in the counterclockwise direction when the solenoidis energized, member 56 need not be employed.

It is thus apparent that both embodiments employ the linearlyreciprocating member as the means to lock the rotary mechanism when thedrive pawl is disengaged from driving engagement with the ratchet wheel.Moreover, both embodiments employ the drive pawl as the means to limitthe amount of rotary motion imparted to the ratchet wheel, thereafterlocking the wheel from further rotation in the drive direction. Thus,rotation of the shaft is fully controlled in direction and amount at alltimes.

Having thus descried my invention, I claim:

1. An improved mechanism for converting linear motion to rotary motionin which the mechanism includes a shaft rotatably supported on a frame,a single ratchet wheel secured to the shaft, a drive pawl adapted toreciprocate into and out of driving engagement with said ratchet wheelmeans, reciprocating drive means connected to said drive pawl to rotatesaid wheel means in one direction and lock means cooperating with saidratchet wheel means to prevent rotation in the other direction, theimprovement comprising:

additional lock means operative to prevent rotation of said wheel meansin said one direction when said drive pawl is out of driving engagementwith said wheel means.

2. The mechanism of claim 1 wherein said improvement further comprisesguide means fixedly supported on said frame adjacent to the path ofreciprocation of said drive means,

said guide means being operative to limit the rotation of said wheelmeans in said one direction when said drive pawl is in drivingengagement with said wheel means.

3. An improved mechanism for converting linear motion to rotary motionin which the mechanism includes a shaft rotatably supported on a frame,ratchet wheel means secured to the shaft, a drive pawl adapted to reciprocate into and out of driving engagement with said ratchet wheel means,reciprocating drive means connected to said drive pawl to rotate saidwheel means in one direction and lock means cooperating with saidratchet wheel means to prevent rotation in the other direction, theimprovement comprising:

additional lock means operative to prevent rotation of said wheel meansin said one direction when said drive pawl is out of driving engagementwith said wheel means; said lock means comprises a lock pawl pivotallysupported on said frame;

said additional lock means comprising a lock bar on said drive means,

said lock bar cooperating with said lock pawl to prevent pivotingmovement of said lock pawl when said drive pawl is out of drivingengagement with said wheel means. 4. An improved mechanism forconverting linear motron to rotary motion in which the mechanismincludes a shaft rotatably supported on a frame, ratchet wheel meanssecured to the shaft, a drive pawl adapted to reciprocate into and outof driving engagement with said ratchet wheel means, reciprocating drivemeans connected to said drive pawl to rotate said wheel means in onedirection and lock means cooperating with said ratchet wheel means toprevent rotation in the other direction, the improvement comprising:

additional lock means operative to prevent rotation of said wheel meansin said one direction when said drive pawl is out of driving engagementwith said wheel means; said additional lock means includes an armprojecting from said drive pawl,

said arm being spaced from said ratchet wheel means when said drive pawlis in driving engagement with said wheel means and in engagement withsaid wheel means when said drive pawl is out of driving engagement withsaid wheel means.

5. The mechanism of claim 4 wherein said wheel nlieafns comprises a pairof ratchet wheels secured to said s a t,

said drive pawl being adapted to engage one of said wheels and said armbeing adapted to engage the other of said wheels. 6. An improvedmechanism for converting linear motlon to rotary motion in which themechanism includes a shaft rotatably supported on a frame, ratchet wheelmeans secured to the shaft, a drive pawl adapted to reciprocate into andout of driving engagement with said ratchet wheel means, reciprocatingdrive means connected to said drive pawl to rotate said wheel means inone direction and lock means cooperating with said ratchet wheel meansto prevent rotation in the other direction, the improvement comprising:

additional lock means operative to prevent rotation of said wheel meansin said one direction when said drive pawl is out of driving engagementwith said wheel means; said drive means comprises a solenoid having areciprocating armature,

a recess in the upper end of said armature,

said drive pawl being pivotally supported in said recess,

spring means in engagement with said drive pawl,

said spring means normally pivoting said pawl toward said ratchet wheelmeans, and

guide means fixedly supported on said frame adjacent the path ofreciprocation of said drive pawl,

said guide means being operative to limit the pivoting movement of saidpawl in a direction away from said ratchet wheel means.

7. An improved mechanism for converting linear motion to rotary motionin which the mechanism includes a shaft rotatably supported on a frame,ratchet wheel means secured to the shaft, a drive pawl adapted toreciprocate into and out of driving engagement with said ratchet wheelmeans, reciprocating drive means connected to said drive pawl to rotatesaid wheel means in one direction and lock means cooperating with saidratchet wheel means to prevent rotation in the other direction, theimprovement comprising:

additional lock means operative to prevent rotation of said wheel meansin said one direction when said drive pawl is out of driving engagementwith said wheel means; said drive pawl is pivotally supported on saiddrive means,

biasing means cooperating with said drive pawl to pivot said drive pawltoward said ratchet wheel means, and

stop means operative to limit the pivoting movement of said drive pawlaway from said ratchet wheel means.

8. The mechanism of claim 7 wherein said stop means is radially spacedfrom the periphery of said wheel means a distance substantially equal tothe Width of said drive pawl.

vent pivoting movement of said lock pawl when said drive pawl is out ofdriving engagement with said wheel means.

References Cited UNITED STATES PATENTS 1,565,336 12/1925 Seufert 741282,900,840 8/1959 Greve 74-1421 2,829,530 4/1958 Holden 74-128 MARK M.NEWMAN, Primary Examiner W. S. RATLIFF, JR., Assistant Examiner US. Cl.X.R. 74126

